<template>
  <div class="pagination">
		<button :disabled="pageNo==1" @click="$emit('getPageNo',pageNo-1)">上一页</button>
		<button 
		v-if="startNumAndEndNum.start > 1" 
		@click="$emit('getPageNo',1)" 
		:class="{active:pageNo==1}"
		>1</button>
		<button v-if="startNumAndEndNum.start > 2">···</button>

		<!-- 中间部分 -->
		<button 
		v-for="(page,index) in startNumAndEndNum.end" 
		:key="index" 
		v-if="page>=startNumAndEndNum.start"
		@click="$emit('getPageNo',page)" 
		:class="{active:pageNo==page}">{{page}}</button>


		<button v-if="startNumAndEndNum.end < totalPage - 1">···</button>
		<button v-if="startNumAndEndNum.end < totalPage" @click="$emit('getPageNo',totalPage)"
			:class="{active:pageNo==totalPage}">{{totalPage}}</button>
		<button :disabled="pageNo==totalPage" @click="$emit('getPageNo',pageNo+1)">下一页</button>

		<button style="margin-left: 30px">共{{total}}条</button>
	</div>
</template>
  
  <script>
export default {
  name: "Pagination",
  // 父组件传递给字符串的数据：当前页，每一页展示多少条数据，数据总个数，连续页码数
  props: ["pageNo", "pageSize", "total", "continues"],
  // 计算属性
  computed: {
    // 总共多少页
    totalPage() {
      // 向上取整
      return Math.ceil(this.total / this.pageSize);
    },
    // 计算出连续页码的起始数字与结束数字[连续页码的数字：至少是5]
    startNumAndEndNum() {
      // 先定义两个变量存储起始的数字与结束的数字
      let start = 0,
        end = 0;
      // 连续页码数字5【就是至少五页】：如果出现不正常的现象【就是不够五页】
      // 不正常的现象【总页数没有连续页码多】
      if (this.continues > this.totalPage) {
        start = 1;
        end = this.tootalPage;
      } else {
        // 正常现象【连续页码5，但是你的总页数一定是大于5的】
        // 起始数字
        start = this.pageNo - parseInt(this.continues / 2);
        // 结束数字
        end = this.pageNo + parseInt(this.continues / 2);
        // 把出现不正常的现象【start数字出现0 | 负数】纠正
        if (start < 1) {
          start = 1;
          end = this.continues;
        }
        // 把出现不正常的现象【end数字大于总页面】纠正
        if (end > this.totalPage) {
          end = this.totalPage;
          start = this.totalPage - this.continues + 1;
        }
      }
      return { start, end };
    },
  },
};
</script>
  
  <style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
.active {
  background: skyblue;
}
</style>
  